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archived-doc-es/appendices/comparisons.xml
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Pedro Antonio Gil Rodríguez 5eed26a161 Actualización a la última versión 
git-svn-id: https://svn.php.net/repository/phpdoc/es/trunk@338594 c90b9560-bf6c-de11-be94-00142212c4b1
2016-02-12 09:53:22 +00:00

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<?xml version="1.0" encoding="UTF-8"?>
<!-- $Revision$ -->
<!-- EN-Revision: e3e2d8a30429ed8b2cc1529409664894b8e5251a Maintainer: seros Status: ready -->
<!-- Reviewed: yes Maintainer: seros -->
<appendix xml:id="types.comparisons" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<title>Tablas de comparación de tipos de PHP</title>
<para>
Las siguientes tablas demuestran el comportamiento de los
<link linkend="language.types">tipos</link> de PHP y los
<link linkend="language.operators.comparison">operadores de comparación</link>,
tanto para comparaciones flexibles como estrictas. Este
suplemento está relacionado también con la sección del manual sobre
<link linkend="language.types.type-juggling">manipulación de tipos</link>.
La inspiración proviene de varios comentarios de usuarios y del trabajo
realizado en <link xlink:href="&url.blueshoes.comparisons;">BlueShoes</link>.
</para>
<para>
Antes de usar estas tablas, es importante entender los tipos y sus
significados. Por ejemplo, <literal>"42"</literal> es un <type>string</type>
mientras que <literal>42</literal> es un <type>integer</type>. &false; es
un <type>boolean</type> mientras <literal>"false"</literal> es un
<type>string</type>.
</para>
<note>
<para>
Los formularios HTML no pasan enteros, reales, o booleanos; solo pasan cadenas.
Para saber si una cadena es numérica, se puede usar
<function>is_numeric</function>.
</para>
</note>
<note>
<para>
Hacer un simple <literal>if ($x)</literal> mientras que <varname>$x</varname>
no esté definido, generará un error de nivel <constant>E_NOTICE</constant>.
En lugar de esto, considere el uso de <function>empty</function> o
<function>isset</function>, y/o inicialice sus variables.
</para>
</note>
<note>
<para>
Algunas representaciones numéricas pueden resultar en un valor representado por la constante
<constant>NAN</constant>. Cualquier comparación flexible o estricta de este valor
con cualquier otro valor, incluyendo a sí mismo, tendrá un resultado &false;,
(esto es, <literal>NAN != NAN</literal> y <literal>NAN !== NAN</literal>).
Algunos ejemplos de operaciones que producen <constant>NAN</constant> son
<literal>sqrt(-1)</literal>, <literal>asin(2)</literal>, y
<literal>asinh(0)</literal>.
</para>
</note>
<para>
<table>
<title>Comparaciones de <varname>$x</varname> con funciones PHP</title>
<tgroup cols="6">
<thead>
<row>
<entry>Expresión</entry>
<entry><function>gettype</function></entry>
<entry><function>empty</function></entry>
<entry><function>is_null</function></entry>
<entry><function>isset</function></entry>
<entry><type>boolean</type> : <literal>if($x)</literal></entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>$x = "";</literal></entry>
<entry><type>string</type></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = null;</literal></entry>
<entry><type>NULL</type></entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>var $x;</literal></entry>
<entry><type>NULL</type></entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><varname>$x</varname> no está definido</entry>
<entry><type>NULL</type></entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = array();</literal></entry>
<entry><type>array</type></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = array('a', 'b');</literal></entry>
<entry><type>array</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = false;</literal></entry>
<entry><type>boolean</type></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = true;</literal></entry>
<entry><type>boolean</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = 1;</literal></entry>
<entry><type>integer</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = 42;</literal></entry>
<entry><type>integer</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = 0;</literal></entry>
<entry><type>integer</type></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = -1;</literal></entry>
<entry><type>integer</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "1";</literal></entry>
<entry><type>string</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "0";</literal></entry>
<entry><type>string</type></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>$x = "-1";</literal></entry>
<entry><type>string</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "php";</literal></entry>
<entry><type>string</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "true";</literal></entry>
<entry><type>string</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>$x = "false";</literal></entry>
<entry><type>string</type></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
<table xml:id="types.comparisions-loose">
<title>Comparaciones flexibles con <literal>==</literal></title>
<tgroup cols="12">
<thead>
<row>
<entry> </entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry><literal>1</literal></entry>
<entry><literal>0</literal></entry>
<entry><literal>-1</literal></entry>
<entry><literal>"1"</literal></entry>
<entry><literal>"0"</literal></entry>
<entry><literal>"-1"</literal></entry>
<entry>&null;</entry>
<entry><literal>array()</literal></entry>
<entry><literal>"php"</literal></entry>
<entry><literal>""</literal></entry>
</row>
</thead>
<tbody>
<row>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>1</literal></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>0</literal></entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>-1</literal></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"1"</literal></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"0"</literal></entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"-1"</literal></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry>&null;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
</row>
<row>
<entry><literal>array()</literal></entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"php"</literal></entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>""</literal></entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
<para>
<table xml:id="type.comparisons-strict">
<title>Comparaciones estrictas con <literal>===</literal></title>
<tgroup cols="12">
<thead>
<row>
<entry> </entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry><literal>1</literal></entry>
<entry><literal>0</literal></entry>
<entry><literal>-1</literal></entry>
<entry><literal>"1"</literal></entry>
<entry><literal>"0"</literal></entry>
<entry><literal>"-1"</literal></entry>
<entry>&null;</entry>
<entry><literal>array()</literal></entry>
<entry><literal>"php"</literal></entry>
<entry><literal>""</literal></entry>
</row>
</thead>
<tbody>
<row>
<entry>&true;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>1</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>0</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>-1</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"1"</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"0"</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"-1"</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry>&null;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>array()</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>"php"</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
<entry>&false;</entry>
</row>
<row>
<entry><literal>""</literal></entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&false;</entry>
<entry>&true;</entry>
</row>
</tbody>
</tgroup>
</table>
</para>
</appendix>
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